From: Anju T Sudhakar anju@linux.vnet.ibm.com
commit 110df8bd3e418b3476cae80babe8add48a8ea523 upstream.
imc_common_cpuhp_mem_free() is the common function for all IMC (In-memory Collection counters) domains to unregister cpuhotplug callback and free memory. Since kfree of memory allocated for nest-imc (per_nest_pmu_arr) is in the common code, all domains (core/nest/thread) can do the kfree in the failure case.
This could potentially create a call trace as shown below, where core(/thread/nest) imc pmu initialization fails and in the failure path imc_common_cpuhp_mem_free() free the memory(per_nest_pmu_arr), which is allocated by successfully registered nest units.
The call trace is generated in a scenario where core-imc initialization is made to fail and a cpuhotplug is performed in a p9 system. During cpuhotplug ppc_nest_imc_cpu_offline() tries to access per_nest_pmu_arr, which is already freed by core-imc.
NIP [c000000000cb6a94] mutex_lock+0x34/0x90 LR [c000000000cb6a88] mutex_lock+0x28/0x90 Call Trace: mutex_lock+0x28/0x90 (unreliable) perf_pmu_migrate_context+0x90/0x3a0 ppc_nest_imc_cpu_offline+0x190/0x1f0 cpuhp_invoke_callback+0x160/0x820 cpuhp_thread_fun+0x1bc/0x270 smpboot_thread_fn+0x250/0x290 kthread+0x1a8/0x1b0 ret_from_kernel_thread+0x5c/0x74
To address this scenario do the kfree(per_nest_pmu_arr) only in case of nest-imc initialization failure, and when there is no other nest units registered.
Fixes: 73ce9aec65b1 ("powerpc/perf: Fix IMC_MAX_PMU macro") Signed-off-by: Anju T Sudhakar anju@linux.vnet.ibm.com Reviewed-by: Madhavan Srinivasan maddy@linux.vnet.ibm.com Signed-off-by: Michael Ellerman mpe@ellerman.id.au Cc: Andrew Donnellan ajd@linux.ibm.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- arch/powerpc/perf/imc-pmu.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-)
--- a/arch/powerpc/perf/imc-pmu.c +++ b/arch/powerpc/perf/imc-pmu.c @@ -1189,6 +1189,7 @@ static void imc_common_cpuhp_mem_free(st if (nest_pmus == 1) { cpuhp_remove_state(CPUHP_AP_PERF_POWERPC_NEST_IMC_ONLINE); kfree(nest_imc_refc); + kfree(per_nest_pmu_arr); }
if (nest_pmus > 0) @@ -1213,7 +1214,6 @@ static void imc_common_cpuhp_mem_free(st kfree(pmu_ptr->attr_groups[IMC_EVENT_ATTR]->attrs); kfree(pmu_ptr->attr_groups[IMC_EVENT_ATTR]); kfree(pmu_ptr); - kfree(per_nest_pmu_arr); return; }
@@ -1327,6 +1327,8 @@ int init_imc_pmu(struct device_node *par ret = nest_pmu_cpumask_init(); if (ret) { mutex_unlock(&nest_init_lock); + kfree(nest_imc_refc); + kfree(per_nest_pmu_arr); goto err_free; } }